This aluminum channel beam compass, with graduations in both inches and millimeters, includes two 13-inch beam bars and one coupling. The maximum arc/ diameter that can be drawn with this compass is 51.5 inches (140.97cm). This specialized compass can be used to transcribe large circles/arcs, transfer measurements on large charts, or technical drawings for wood or metalwork projects. A molded storage tray holds all the components in place when not in use. A 13-inch (33.02cm) Extension Bar (545330) enables the user to extend the reach of the compass to a 64-inch (162.56cm) radius when using all extension bars. (Available separately.) Includes: Two 13-inch aluminum beam bars Two slide assemblies with thumbwheel Cutting blade insert (mounts in slide assembly) Full-sized pencil/ pen adapter (mounts in slide assembly) Two spare points/ lead Two point holders Lead sharpener Molded storage tray Made in Germany Lifetime warranty